Control system for elevators



Aug. 14, 192s. 1,680,771

L. l. DAVIS CONTROL SYSTEM FOR ELEVATORS Filed March 9, 1926 3 Sheets-Sheet l f W l 20/ 15107/ P200 xzoa 204 255 ,Lczaa @2i/154 202i 36 224 /6222 F225 P227 f a 0 v 2/0 022/7 022/0 X220 H120 l 0195 0R24 M232 3 Sheets-Sheet 2 L. l.` DAVIS CONTROL SYSTEM FOR ELEYATORS Filed MaICh 9, 1926 Z4Z\ LC/Z/ H/ZZ Aug. 14, 192s.

Aug. 14, 192s. v1,680,771

L. l. DAVIS CONTROL SVYSTEM FOR ELEVATORS Filed March 9, 1926 5 Sheets-Sheet 3 56W LHO? Patented Aug. 14, 1928.

UNITED STATES 1,t8tl,771 PATENT FFME.

LEE I. DAVIS, F' YORK, N. Y., ASSIGNOR TO OTIS ELEVATOR COMPANY, 0F JERSEY CITY, NEW lJERSEY, A CORPORATION 0F NEW' JERSEY.

CONTROL SYSTEM FOR ELEVATORS.

Application filed March 9, 1926. Serial N'o. 93,4551.

The invention relates to control systems and particularly to control systems for elevators.

Y In elevator control systems where the elevator motor is supplied with current by a variable voltage generator, the generator 1s required to operate over a wide rangeaof E.

' M. F. values varying from a maximum in one direction to a maximum in the other.

Where self-leveling apparatus is employed,

the generator is required to operate at low values of E. M. F. in bringing the car to a level with a. desired landing. Due to the residual flux of the generator iield, the E. l5 M. F. values obtained for a iven value of field current during thelleve ing operation vary considerably, depending .on the magnetic state of the machine prior to leveling and whether the car is approaching the landing or returning to the landing after an overrun. Such variations in E. M. F. values must be taken into account inthe o eration of the car during the leveling perio Furthermore, the amount of loadin the elevator cardis also a factor which must be considere The principal object of the invention is to cause .more uniform operation of the elevator car during the leveling period;`

One feature lof the invention is to compensate or the residual flux of the genera- -tor field during the leveling period when the effects of the residual flux would y"be detrimental to the leveling operation.

Another feature yof the invention. resides in compensating .for the load in the elevator car durind the leveling period.

'Other eatures and advantages will becomel appa-rent from the following description, taken in connection .with the accompanyingdrawings wherein the invention is embodied in' concrete :form and in which:

Figure* 1 is a diagram of an elevator control system;

Figure 2 is a schematic representation of the elevator car at alanding, illustrating the arrangement of the car switch and of mechanism'suitable for etecting the leveling and car gate and hatchway door opening opera- 50 tions; v l Figure 3 is a hysteresisl curve employed to illustrate the invention; v

'Figure 4 is a portion of a diagram, similar to Figure 1, of another arrangement of the control system;

Figure' is a portion of a diagram, similar to Figure 1, of still another arrangement of the control system; and

Figure 6 is a portion of a. diagram, similar to Figure 1, of still another arrangement of the control system.

Referring to Figure 1, no attempt is made to showthe coils and contacts of the various electromagnetic switches in their associated positions, a straight diagram being employed wherein the coils and contacts of the various switches are separated in such manner as to render the circuits involved relatively simple. Also the parts of other switches and apparatus are separated in the interest of simplif ing 'the diagram. It is to be understood that the system in which the invention is illustrated is chosen merely ifor convenience of description and that, a1- though described in conjunction withv a car switch controlled system, the invention is equally applicable to other types of elevator systems such as push button control systems and to other systems employing a work motoi supplied with current from the generator 80 of a motor generator set.

The motor generator set comprises a driv- -ing motor 11, illustrated for convenience of description as of the direct current type, and a variable voltage direct current generator 12. The armature ofthe driving motor Yis designated 13 and its eldwinding`l4. The armature of the generator is designated 15, its series field winding '16, its main separately excited field winding 17 and its auxiliaryseparately excited iield winding' 18. The elevator motor is designated as a whole by the numeral 20, its armature being designated -21 and its lield winding 22. An adjustable resistance 23 is arranged in shunt to the generator series field winding. Discharge resistances 24 and 25 are provided for the generator separately excited tield windings 17 and 18 respectively. .Discharge resistance 26 is provided for the elevator mo- 100 tor field windlng 22. A resist-ance 27 is provided for controlling the strength of the generator field and therefore the voltage applied to the elevator motor armature during different conditions of operation. 30 is the release coil for the elevator motor electromagnetic brake. This coil is provided with discharge resistances 31, 32 and 33 for controlling the application of the brake under different conditions of operation. 34 and 35 are the up slow speed contacts and the down slow speed contacts respectively of the leveling switch, the leveling .switch up and down fast speed contacts being designated 36 and 37 respectively. 38 is the armature and 40 is the field winding of the motor 41 for moving the rollers of the leveling switch into position to clear the leveling cams. 42 is the armature and 43 is the field winding of the door control motor 44. 45 and 46 are the direct current supply mains. 47 is a double pole knife switch for connecting the system to the supply mains. In order to suit the type of diagram employed, the blades of this switch are shown separated. The car switch is designated as a whole by the numeral 48. 50 is the safety switch in the car. The series of door contacts are indicated bya single set of contacts 51. The gate contacts are indicated as 52. The varions safety, limit, stop and emergency switches are omitted in order to simplify the description. i

The electromagnetic switches have been designated as -followsz A-potential switch,

B-up main direction switch,

Cdown main direction switch,

D--first accelerating switch,

E-second accelerating switch,

F-series field switch,

Ge-series field relay,

H-main brake and field switch,

J-door control switch,

K-door control motor maintaining relay,

M-maintaining relay,

N-sequence relay,

O-accelerating relay,

P-hard brake switch,

UR-fu'p residual compensating switch,

DR- down residual compensating switch,

LB;up'leveling direction switch,

LC-down leveling direction switch,

LH-leveling brake and field switch,

LF--fast speed leveling relay.

Throughout the vdescription which follows, theseletters, in addition to the usual referencenumerals, will be applied tothe parts of the above enumerated switches. For

example, contacts B111 are contacts on the',

up main direction switch, while actuating coil A53 is the coil that operates the potential switch. The electromagnetic switches are shownv in their deenergized positions. Reactances rare similarlydesignated by the character X.

Upon the closing of the knife switch 47, the driving motor 11, elevator motorv field wlnding 22 and potential switch actuating coil A53 are energized, the .circuit for coil A53 being through safety switch 50. ,The driving motor starts in operation, bringing the generator 12 up to full speed. The series field winding and starting means for the driving motor are omitted to simplify the description. With the elevator motor at rest, the current supplied to its field winding 22 is reduced by section 54 of resistance 29, providing what may be termed a standing field. The circuit for 'the elevator motor field winding may be traced from the left-hand blade of, switch 47 line55, by Way of line 56 through field winding 22, resistance section 54 and second' accelerating switch contacts E57, line 58, to the righthand blade of switch 47. It is not desired to apply full line voltage to the field winding 22 when the elevator motor is not in operation because of increased power consumption. On the other hand, it is not desired to have this field winding deenergize with the elevator motor at rest as a matter of safety and because of the time constant involved in lbuilding up. The potential switch, upon operation, causes the engage-` ment of contacts A60 and A61, preparing the circuit for the generator separatel excited field winding, the electromagnetic brake release coil and the control circuits. The condition of the circuits so far described might be termed normal.

Referring briefiy to "Fi ure 2, the car switch 48 comprises a set o up contacts 62,

63, 64, and 66 and a Set of down contacts 67, 68, 69, and 71. A contact segment 72 for bridging the contacts of each set is mounted on the segmental support 73 of insulating, material. A. cam 74 is formed on the support above the pivot point 75. The cam is formed with a centrally disposed depression 76 into which the ,operating roller 77 of the gate and doorn switch 78 extends with 'the car switch in neutral or off position. The switch 78 is pivoted at 80 so that movement of the car switch in either direction causes the engagement of the switch contacts. The car switch is operated by means o f a control handle 81. It is preferred to provlde centering springs (not shown) on off position when released by the operator.

Referring back yto Figure 1, assume that the system is designed for an installation of several fioors and that the car is at rest at the first floor with the gate and door open. In the starting operation, the operator first gives the car switch a slight initial movement to. effect the closure of. the gate and door switch 78. For convenience of description, this switch is arranged to complete Va circult for the door control 'motor switch actuating coil lJ82. This circuit may be traced from the left-hand blade of switch 47, by way' of line 55 through contacts A60,

an Y

lll() the car switch to cause it to be returned to Lesern control motor field winding 43 and armature 42, by wa of line 58 through contacts A61, to the rig it-hand blade of switch 47.

Referring again to Figure 2, motor 44 operates pneumatic gateand door operating mechanism, as for example through linkage 90 to move valve 91 for gate engine 92 to gate closed position and to withdraw the retiring cam 93 from engagement with the roller provided onthe end of the door engine valve lever 94. The lever `94 is operated by a spring to move valve 95 for the l door engine 96 to door closed position. The gate and doorl engines operate through mechanism not shown to close the car gate 99 and hatchway door 109. It is to be understood 'that a door is provided inf the hatchway at each landing.

Referring back to Fi ure'l, if the operator, after he has close the gate and door, desires to open them, or if he desires' to arrest their movement, he may do so by releasing the car switch to return to oil position. This causes the opening of the gate and door switch 78 with the consequent deenergization of coil J82 and the separation of contacts J87. In this manner, the circuit for the motor 44 is broken. The spring 97, shown in Figure 2, operates upon the deenergization of motor 44 to move valve 91 and, through cam 93 and lever 94, valve 95 into positions to cause the reverse operations of the engines 92 and 96 to openthe gate and door. Obviously other forms of` power operated gate and door mechanisms, such as electric vin lieu of pneumatic, may be employed .without departing from. the spirit of the present invention.

Assuming that the gate and doors are closed, the gate contacts 52 andfdoor contacts 51 are in engagement. The operator may now move the car switch to full operated position to start the car in the up direction. It is to .be'not'ed that the gate and `door switch 78 remains'in closed position so ,long as the car switch is moved out of neutral position. Upon the engagement of contact segment 72 and contact 64, circuits are 'simultaneously completed for thev oppositely wound v'coils N98 and N100 of the sequence relay, actuatingv coils H101fofl the main brake and field switch and B102 of the up mainv direction switch being in the circuit for oeil N100. The engagement of the contact segment. and contacts and 66 prepares circuits for the actuating coils of the accelerating switches.

The circuit for coil N98 of the sequence relay may be traced from the left-hand blade of switch 47, by way of line 55 through contacts A60, by way of line 103` through coil N98 and resistance 104, contacts 62 and 64 of the car switch, by way of line 105 through contacts C106 of the down main direction switch,'line 85, to the right-hand blade of switch 47 as above traced;v The circuit for coil N100 may be traced from the left-hand blade ot' switch 47, by way of line 55 through contacts A60, by way oi'I line 107 through door contacts 51, gate contacts 52, sequence relay contacts N108, and lcoils N100, H101 and B102, contacts 63 and 64 of the car switch, to the right-hand blade of switch 47 as above traced. The purpose of the sequence relay N is to insure the closure of the gate and doors before starting the car. Coils N98 and N100, being diiferentially wound, oppose each other, when energized simultaneously, to prevent the operation of the relay. If either coil is energized ahead of the other, or if eithercoil alone is energized, contacts N108 separate, preventing the starting ofthe car. 4If either the gate contacts 52 or any of the door contacts 51 are. separated at the time that car switchl segment 72 engages contacts 64, coil N98 alone is energized, resulting in the separation of contacts N108. The separation of contacts N108 prevents the energization of coil N100, maintaining the' sequence relay operated, and of coil B102, preventing the operation of the up main direction switch to effect the starting of the car. The gate and door switch 78, therefore,.is close-d by the initial movement of the car 'switch so that the gate and door contacts may be closed before the engagement of segment 72 and contact 64. However, if the car switch is moved into position -'where segment 72 engages contact 64 before the closure of the door and gate contacts, the sequence relay operates to prevent the starting loit' ythe car. Thus it is impossible to start the car on the door or gate contacts.

vAssuming that the sequence relay has operated, in order to start the car,.the car switch isr returned to 4a position with segment -72 disengaged from contact 64, deenergizing coil N98 to permit contacts N108 to reengage.

If the gate and door vare closed, the car switch may be returned immediately to full on position. Otherwise, 'closing of the gate and door must be eii'ected before the car switch is moved into full on position.

It is preferred to provide the main direction switches with a mechanical interlock to prevent their simultaneous operation. Such an interlock may be of the form of a walking beam pivotally mounted for engaging catches on the armatures of these switches.

lIU

liti

Upon operation of the up main direction switch in response to the energization of its actuating coil B102, contacts B110 separate and contacts B111, B112 and B113 engage. The separation of contacts B110 breaks the circuit leading from the car switch down feed contact 69, contacts B110 and the corre-y sponding down direction switch contacts C106 serving .as electrical interlocks. The engagement of contacts B113 prepares the circuit for the up main direction switch holding coil B115 andv the main brake and field switch holding coil H116. The engagement ofconta'cts B1114 and .B112 completes a circuit for the generator main field `winding 17. This circuit "may be traced from the left-hand blade of switch 47, by'

way of line 55 through contacts A60, resist-ance 27 and contacts'Blll, by way of line 117 through field, winding 17, by'way of' line 58 through contacts B112 and contacts A61, to the right-hand blade of switch 47.

The main brake and field switch H' operates simultaneously with the main direction switch B. Switch H, upon operation, causes the separation of contacts H119, H122 and H123 and the engagement of contacts H120,

H124, H125, H126 and H127. The separaltion of contacts H119 disconnects the generator main field winding `from the generator armature. The purpose of this arrangement will be explained later. Gontacts H122 are in the circuit for the generator auxiliary field winding 18. The purpose of thisarrangement also will be explained later. The separation of contacts H123 disconnects resistance 33 from across the brake releas( coil 30. Resistance 33 being of low ohmic value, its disconnection be- |fore contacts H124 engage prevents excess power consumption from mains 45 and 46. The engagement of contacts H120 completes the circuit for up -residual compensating switch holding coil UR217 and down residJ ual compensating switch'holding coil DR218. This circuit maybe traced from the lefthand blade of switch 47 'by way of line 55 through contacts A60, by way of line 216 through coil UR217, coil DR218, reactance y X220 and contacts H120, by way of line 58 through contacts A61, to the right-hand blade of switch 47. The magnetizing forces exerted by these coils are insufficient to cause the operation of the switches. The purpose of this ,arrangement will be seen from later description. The `engagement of contacts H127 establishes a circuit for the door control motor maintaining 'relay actuating coil K130. This circuit may be traced from the left-hand blade of switch 47 by Way of line '55 through contacts A60, by way of line 83 through coil J 82, by way of line 131 through up leveling direction switch contacts LB132, down leveling direction switch contacts 110133,v contacts H127- and coil K130, line 85, -to the right-.hand blade of 134 through contacts 135 operated bythe. brake, brake release coil 30 and-contacts H124, by way of line 58 throughcontacts A61, to the right-hand blade of switch 47.

The door control motor maintaining relay coil K130 in the circuit above traced is subject to' the potential drop across resistance 84. The system is arranged so that the voltage thus applied to coil K130 is sufficient to -e'fi'ect the operation of the relay. Contacts K136 engage, upon the operation of the relay, to by-pass contacts H127. The purpose of this arrangement will be seen ,from later ing supplied from the generator armature- 15 to the elevator motor armature 21, due to the energization of the generator main field winding, the elevator motor starts.

As the brake releases, the brake switch contacts 135 separate to insert cooling resistance 137 in series with the brake release coil. These brake switch contacts are preferably arranged to be separated at the end of the releasing operation. Separation of contacts 135 also breaks the short circuit around coil 0138.I permittin the operation of the accelerating relay This relay operates to cause the engagement of contacts 0140, completing the circuit for the first-accelerating switch actuating coil D141. The purposeof this arrangement is to utilize the time constant of the brake 4for timing the acceleration of the motor, more specifically, for timing the operationof the first accelerating switch. Although the'brake release coil is energized at the same time that power is supplied to the motor, the brake shoes do not lift at once because of the inherent time constant 'of the brake magnet and because the brake shoes and lever arms represent door contacts 51, gate contacts 52 and contacts N108, by way of line 142 through contacts H125, contacts 0140 and coil D141,

switch, in response to the energization of its actuating coil, causes the engagement of contacts D143, D144, D145 and D146. The engagement of contacts D143 completes the circuit for the leveling switch motor 41. This circuit may be traced from the left- 4hand bla-de of switch 47 by way of line 55 through contacts A60, by way of line 147 through contacts D143, lieldwinding 40 and armature 38 ozt moto-r 41, by yway or line 58 through contacts A61, to the right-hand blade of switch 47. The leveling switch motor, upon energization, acts to move the leveling switch operating rollers so as to clear the leveling cams during movement of the car. This operation will be explained later. The engagement of contacts D144 completes the circuit for holding coils B115 and H116. This circuit may be traced from the lefthand blade of switch 47 by way of line 55 through contacts A60,'by way of line 148 through coil H116 and contacts D144, by way or' line 150 through coil B115 and contacts B113, line 151, line 85, to the righthand blade of. switch 47 i as previously traced The purpose of the energization or' these holding coils will be seen from later description. The engagement of contacts D146 completes the circuit for the second accelerating switch actuating coil E152. This circuit may be traced from the lefthand blade of switch 47 by way of line 55 through contacts A60, by way of line 107 through door contacts 51, gate contacts 52 and contacts N108, byl 'way of line 142 through contacts H125, by way of line 153 through contacts D146, reactance X154 and coil E152, car switch contacts 66 and 64, to the right-hand blade of switch 47 as previously traced. The engagement of contacts D145 short-circuits section 155 of-resistance 27, increasing the voltage applied to the generator main field winding. Thus the genera-- tor E. M. F. lis increased, increasing the speed of themotor.

The secondaccelerating switch E does not yoperate immediately the circuit for its actuating 'coil' is completed, its action being delayed by the effect of reactance X154. Upon operation, contacts E156 and E57 separate and contacts E157 and E158 engage.l

The separation of contacts E156 removes the shunt circuit around a portion of resistance 160. The separation of 'contacts E156 before contacts E158 engage prevents excess-power consumption from mains'45 and 46., The engagement of contacts E158 completes the circuit for the lirst accelerating switch holding coil D161 and the maintaining relay actuating coil M162. This circuit Inay be traced' from the left-hand blade of switch 47, by way of line 55 through contacts A60, by way of line 151 through con tacts E158, reactance X163, coil D161 and coil M162, line 85, to the right-hand blade of switch 47 as previously traced. The maintaining relay contacts M164 are thus caused to by-pass contacts D144. The purpose of this 'arrangement will be described later. The engagement of' contacts E157 short-circuits section 165 of resistance 27. to increase the voltage applied to the. generator main field winding. The E. M. F. of the generator, therefore, increasesto its full value and the speed of the elevator motor increases.

. The separation of contacts E57 removes the short circuit for section 167 of resist-ance 29 in the elevator motor field winding circuit, bringing the elevator motor up to full speed.

The residual compensating switches are polarized by means of the holding coils UR217 and DR218 which are connected to the mains so long as the car is running subject to either car switch or leveling switch control. The actuating 'coils UR118 and DR121 of these switches are connected across the generator armature. The connection for coil UR118 is such that, when the generator field winding is energized to cause the generation of an E. M. F. for up motion of the car, coils UR118 and UR217 act cumulatively and cause the operation of the up residual compensating switch when the generator E. M. F. rises to a predetermined value. Similarly, the connection for coil DR121 is such that, when the generator ield winding is energized to cause the generation of an E. M. F. for down motion of the car, coils DR121 and DR218 act cumulatively and cause the operation of the down residual compensating switch when the generator E. M. F. rises to a predetermined value. It is to be understoodthat the coils may be so designed that the respective switches will operate at lany predetermined value of generator E. M. F. Since up motion of the car has been described, the switch UR operates, upon the generator E. M. F. rising to t-he predetermined value, to cause the separation of contacts UR240. The separation of contacts UR240 insert-s up residual compensating resistance 19 in the circuit for field winding 18 to be completed'in the operation of. bringing the car to a level with a landing upon an underrun with the car moving in the up direction. The purpose of this arrangement will be set forth inplater description.

The starting of the car in the down direc-v down main direction switch actuating coil C168. This circuit may be traced from the left-hand 4blade of switch 47, through coil H101 as previously traced, by way of line 170 through coil C168, car switch contacts 68 and 69, by way of line 171 through contacts B110,

line 85, to the right-hand blade of switchy 47 as reviously traced. The circuit for coil N98 is by way of line 172. The circuit for coil D141 is by way of line 173. The circuit for coil E152 is by way of line 174. The down main direction switch, upon operation, causes the separation of contacts C106 and the engagement of contacts C175, C176 and C177,

these contacts corresponding with up main direction switch contacts B110, B111, B112 and B113 respectively. The holding coil of the down main direction Vswitch is designated The down. residual y compensating switch DR I operates to separate contacts DR241. The separation of these contacts inserts down residual compensating resistance 39 in the circuit for field winding 18 to be e completed in the operation of bringing the car to a level with a landing upon an underrun with the car moving in the down direccoil E152, first accelerating switch actua-ting coil D141, main brake and field switch actuating coil H101, up 4main direction switch actuating coil B102 and sequence relay coils N98 and N100 arebroke'n. The second accelerating switch drops out immediately. The first accelerating switch, main brake and field Switch and up main direction switch are maintained operated, however, by holding coils D161, H116 and B115`respectively. The deenergization of coils 'N98 and N100 is in preparation for the next starting operation It is 'to be noted that switch 78 is opened `by the centeringjof the car switch. The circuit for coil J 82, however, is maintained through (Izntacts H127 and K136 in parallel and 'coil TheI second accelerating switch, upon dropping out, causes the separation of con' tacts E157 and E158 and the reengagement of contacts E57 and'E156. The separation of contacts E157 reinsertssection`165 of resistance 27 in series with the vgenerator main separately excite-d 'field' winding to decrease ,the E. M. F. of the generator.

The engagement of contacts E57 short-circuits section 167 of resistance 29, increasing vthe strength of the elevator motor field for the stopping car is running in the up operation. With the -generator E. M. F. lowered and the strength' of the elevator motor field increased, the speed of the elevator motor is decreased. The se aration of "contacts E158'breaks the circuit or holding coil D161 and coil M162. The first accelerating switch vD and maintaining relay M do notdrop. out immediatel however,

their action being .delayed by t e effect of i lreactance X163 in series with the coils and struction than the accelerating switch and f requires less current to holdin.

The first acceleration switch, upon dropping out, causes the separation of contacts D143, D144, D145 and D146. The separation of contacts D144 is in preparation for the next starting operation, contacts M164 remaining in engagement to maintain'holding coils H116 and B115 energized. The separation of contacts D146 also is in preparation for thenext starting operation, the circuit for coil E152 having been broken by the movement of the car switch as above described. The separat-ion -of contacts D145 removes the short circuit for section 155 of resista-nce 27, decreasing the strength of the generator field. Thus the r vnerator` E. rM. F. is again decreased and t e speed of the elevator motor is reduced.

The separation of contacts D143 deenergizes the leveling switch motor 41.` In this manner the operating rollers of the leveling switch are extended for engagement bythe leveling cams. Referring briefly to Figure 2, theleveling switch motor is operatively connected to the leveling switch by means of an arm 180 on the motor shaft, a connecting link 181 and a lever 182. In the starting operation, the motor 41 being energized, arm 180 rotates, acting through link 181 and lever 182 to move the leveling switch as a whole about a pivot. In'this manner the leveling switch operating rollers 183 and A184 are moved into position where they do not engage the leveling cams 185 and 186 during motion of the car, a stop being' provided to,

determine the extent of the movement. It is to be understood that leveling cams are provided for each Yfloor. The leveling switch is pivoted on a bracket 187 secure-d vto the car frame. In the stopping operation, upon the deenergization of the leveling ncaav'n switch motor,'a spring (not shown) moves `the lever 182 and therefore the leveling of leveling switch contacts 34, 35, 36 and 37 comprises a stationary contact and a movable contact operated by the engagement of its corresponding roller andv leveling cam. The fast speed contacts 36 and 37 are' arranged to separate before their corresponding slow speed contacts 34 and 35 in the levelingl operation. Springs (not shown) are provided for 'causing the separation of the -contacts, of the pairs as the leveling operationis effected and stops are provided for determining the extent of movement of the rollers as they ride oit/the leveling cams. p

Alt will be assumed that: the car has not reached the landing and that the up leveling switch operating roller 183 moves onto the xvertical surface loit up leveling cam 185 before relay Ilvl drops out. The/engagement of leveling switch up slowspeed contacts 34 completes a circuitltor the up leveling direction switch actuating coil LB188 and the leveling brake and field switch actuating coil LH190. This circuit ma v be traced from the left-hand blade of switc 47, by.` way of line 55 through contacts A60, line 191, leveling switch contacts 34, by wayofline 192 through coil LB188 and coil 'LH190, line 85,

` to the right-hand blade of switch 47 as previ` ously traced. t The engagement of the leveling switch up fast speed contacts 36 completes the circuit for fast speed leveling relay actuatingcoil LF193. This circuit may be traced from the left-hand blade of switch 47, byl way of line 55 through contacts A60, line 191, leveling switch contacts 34, line 194, leveling switch contacts 36, by way of line 85 through coil LF193, to the right-hand blade of switch 47 aspreviously traced. It

l is to be noted that, due to the fact that the circuit for coil 'LF193 is through leveling switch slow speed contacts 34, the circuit for coils LB188 ,and LH190 must be made -in order that the circuit for coil LF193 may be completed. y

The up leveling direction switch LB, upon operation, 'causes the separation of contacts LB132 and the engagement of contacts LB195, LB196 and LB197. Contacts LB132 will be referred` to later. Contacts LB195 and LB196 prepare a circuit for the gen` erator auxiliary separately excited field winding 18. The engagement of contacts LB197 completes the circuit for up series iield relay actuating coil G198 and up hard brake switch actuating coil P200. This cir cuit may be traced lfrom the left-hand blade of switch 47, by way of line 55 through contacts A60, by way of line 201 through contact-s LB197, coil G198, coil P200, and portion 202 of reactance X203, line 204, by way of-line 58 through contacts 14.61,'to the righthand blade of switch 47.

'Ihe leveling brake and field switch, operating simultaneously with the. up leveling direction switch, causes the separation of contacts LH205, LH206 and LH212 and the 'engagement' of contacts LH207, LH208 and LH210. Contacts LH205 are in the circuit for resistance 33 across the brake release coil. Contacts LH206 are in series with contacts H119 in the circuit for connecting the. generator separately excited field winding to the generator armature. Contacts Lll212rbreak the shunt circuit, comprising resistance 160, for coils D161 and M162. Contacts lLH207 by-pass contactsH124 in the circuit for the brake release coil. Conta-cts`LH208 by-pass contacts H126 `in the circuit for section. 54 of the motor field resistance 29. Contacts LH210 by-pass contactsH120 in the circuit for the holding coils of the residual compensating switches. The purpose of contacts LH205, lil-1206, LH207, LH208, LH210 and .Ll-1212 will be seen as the description proreeds.

he fast speed leveling relay, upon,l operation, causes the LF213 and LF214. The engagement of contacts LF213 short-circuits resistance 28 employed during leveling to reduce theflow oi' current through the generator auxiliary field winding for slow speed operation. Thev engagement ofr contacts LF214 ley-passes switch 78, as Well as contacts LB132, LC133, y

H127 and K136 and coil K130 through resistance 84, in a circuit for coil J82 of the door control motor switch. Since the engagement of contacts LF214 generally occurs substantially simultaneously with the separation of contacts LB132, the switch J does not drop out. Even if switch J should drop out, the immediate reenergization of coil `J 82 upon the engagementof contacts LF2-14 would prevent the operation of the gate and door operating mechanism due to 'the time required for 'the mechanism' to start in' operation. The circuit for the door control motor maintaining relay coil X130, however, is broken by the separation of contacts LB132.

The separation of contacts LH212 to break the circuit for resistance 160 as above Set `forth causes relay M to drop out and separate contacts M164. As a resultthe circuit 4for holding coils B115 and H116 is broken,

engagement of contacts lll ever, the auxiliar field winding is simultav neously connecte l to the mains by contacts H122 of the main brake and field switch H as set forth below. The switch H, upon dropping out, causes the separation of contacts H120, H124, H125-, H126 and H127 and the engagement of contacts H119, H122 and H123. The separat-ion of contacts H125 and H127 is in preparation for the next starting operation. The separation of contacts H120 is without effect as the circuit for the residual compensating vswitch holding coils is maintained by contacts LH210. The magnetizing force exerted by each Iof these holding coils is sufficient to maintain .its switch, once operated, in operated condition. Thus, in the present example, contacts UR240 in the shunt circuit for up residual compensating resistance 19 are maintained separated. The separation of contacts H124 and H126 is witho-ut effect, the circuit for the brake release coil 30` being maintained by contacts LH207 and section 54 of resistance .29 remaining short-circuited by con*v tacts LH208. The engagement of contacts H119 and H123 also-is Without effect as the circuit for reconnecting the main separately excited field winding to theigenerator armature is maintained'broken by contacts LH206 and the shunt circuit for the bra-ke releasey coil 30 comprising resistance 33. is ymaintainedbroken by contacts LH205. The engagement of contacts H122, however, completes the circuit for the auxiliary field winding 18. This circuit may be traced from the left-hand blade of switch 47, by way of line 55 through contacts A60, by way of line 215 through contacts H122 and contacts LF213, byfway of line 242 through contacts LB195 and resistance 19, through field windin 18, back to line 215 through contacts L 196, by way of line 58 through contacts A61, tothe right-hand blade of switch 47. With contacts LF213 in engagement, shortcircuiting resistance 28, and with up residual compensating resistance 19 in circuit with the auxiliary field winding, an E. M. F. is generated which causes the elevator motor to run at a suitable fast leveling speed. Discharge resistance 24 acts not only to smooth out the changes in generator E. M. F. due to the reinsertion of resistance 27 in circuit with the main field Winding in steps but also acts to prevent a sudden drop in value of the E. M. F. upon changing over from the mainto the auxiliary field winding. It is to be understood that resistance 27 may be controlled in any number of steps, two beingshown merely for convenience of description.

Relay vGr and switch P do not operate immediately their actuating coils are energized, their action being delayed by reactance X203. Swltch P, however, is adjusted to operate almost immediately and, upon operation,

tion, causes the engagement of contacts G222, completing the circuit for the series .field switch actuating coil F223. `This circuit may be traced from the left-hand blade of switch 47, by way of line 55 through contacts A60, by way of line 224 through contacts G222 and coil F223, by way of line 58 through contacts A61, to the right-hand blade of switch 47. Switch F, upon operation, causes the separation of contacts F225. breaking the circuit including resistance 23 in shunt to t-he generator series field winding 16. The generator series field is so wound that, Without the parallel resistance 23, it would have too great an effect for proper operation of the car. The desired compounding is obtained by employing the low i resistance shunt. Upon separation of contacts F225, the strength of the series field is increased for the leveling operation so as to aid in bringing the motor to a stop. The short delay in the action of relay G, and therefore switch F, upon theinitiation of the leveling operation, is desirableV in order that the current in the generator armature-elevator motor armature circuit may adjust itself to such a value that proper series field 95 strength during the leveling operation may be obtained.

As the car nears the third fioor landing, roller 183 rides ofi the vertical surface onto the oblique surface of cam 185. This re- 10u sults in the separation of leveling switch up fast speed contacts 36, deenergizing fast speed leveling relay coil LF193. Relay LF, upon dropping out, causes the separation of contacts LF213 and LF214. The separation of contacts LF213 removes the short circuit f for resistance 28. Resistance 19 remains in circuit with the auxiliary field winding due to the fact that contacts LH210 are maintained in engagement. The generator E. M. F. is thus lowered and the elevator motor runs at its slow leveling speed. The separa tion of contacts LF214 breaks the circuit for the door control motor switch coil J82. Switch J, upon droppingl out, causes the separation of contacts J 87 to deenergize the motor 44, thus effecting the automatic gate and door opening operation. The gate and door operating mechanism functions in the same manneras described for opening the gate and door in response to centering the 'car switch. In this manner the automatic gate and door opening operation is timed so that the gate and'door open as the car stops at the landing. It is' to be noted, however, 125 that the automatic gate and' door opening operatlon cannot take place until the levellng switch fast speed contacts separate. y Shortly before the car reaches the exact level with the landing, the roller 183 rides 130 tion.

oi the oblique surface-of cam A185, therebyV separating the leveling switch up slow speed contacts 34. The circuit for coils LB188 and LH190 is thus broken. Switch LH drops out, causing 4the separation of contacts LH207, LH208 and LH2l0 and the reengagernent of contacts LH205, LH206 and LH212. The engagement of contacts LH212 is in preparation for the next starting operation. The separation of contacts `)Ll-.i207 breaks the circuit for the brake release coil 30, effecting the application of the brake. The separation of contacts LH207 also breaks the circuit for the accelerating relay coil 0138. The accelerating relay 0 drops out, separating contacts 0140 in preparation for the next starting Operation. The separation of contacts LH208 reinserts section 54 of resistance 29 inzseries with the elevator motor, field winding, current therein to a standing field value. The separation of contacts LH210 breaks the circuit for holding coils UR217 and DR218 of the residual compensating switches, switch UR dropping outto cause the reengagement of'contacts 'UR240 to short-circuit resistance 19. It is to be noted that the dropping out of switch UR is delayed due to the action oi' reactance X220 in series with coil UR217 and discharge resistance 128 in parallel with the reactance and coil. The purpose of this arrangement will be seen from later descrip- The reengagement of contacts LH206 reconnects thegenerator mainfield winding to the generator armature. The polarity of `this connection is such thatthe generator vsends current through'the field winding in such manner as to oppose the iuX .which produces the generator E. M. F., thus tending to -destroy the residual iuX of the generator field.

l Upy leveling direction switch LB, drop- 1 ping out simultaneously with switch LH,

causes the separation of contacts 1113195, LB1'96` and LBlQ' and the engagement of contacts `LB132. The engagement of contacts LB132 is in preparation for the next Istarting*operation The Vseparation of contacts LB195 and LB196 disconnects the generator auxiliary field winding from the mains, the main field winding being simultaneously connected to the generator armature by contacts LH206, as set forth above. The separation of contacts LB197 breaks the circuit for coils G198 and P200. rThe relay G drops out immediately but the dropping out of switch P is delayed slightly due to the effect of the reactance X203 and discharge resistance 226. It is to be noted that the discharge current for up coil P200 and thereactance passes through down coil P227 in such direction as to cause coil P227 to assist-coil P200 in maintaining switch P in operatedv condiftionl Relay G, upon dropping out, causes the separation of contacts reducing the l G222 to deenergize coil F223, switch F dropping out in turn to cause the engagement of contacts F 225. The engagement of contacts F225 reconnects resistance 23 in parallel with the generator series field winding 16. Switch P, upon dropping out, causes the engagement of contacts P221.

Thus the brake being applied and the generator separately excited field windings being disconnected from the mains, the car is brought to rest level with the third door landing.` Since the engagement of contacts P221 is delayed, the brake lrelease coil 30 discharges only into resistance 31 of relatively high yohmic value and a hard application of the brake is obtained. -ln this nianner a assured.- y l With the sequence of operations as above described the car willl belslowed 'down and stopped level with the desired landing without sacriiiceof smoothness. However, should the car switch be centered with the car at a greater distance from the landing, the maintaining relay would hold in to effect, through its contacts M164, the retention of themain positive stop at the landing is direction switch and main brake and field L switch in operated condition. Should relay M 'drop out before the leveling switch contacts engage, the subsequent engagement of the leveling switch contacts as the leveling switch roller rides onto thecam would cause the operation of switches LB and LH and relay LF to bring the car to a level with the iioor. In the event that the car switch is centered late in the stopping operation, as for example when the leveling switch operating roller strikes the leveling cam upon the dropping out of the first accelerating switch D, the Vimmediate separation .of Kcontacts LH212 forces the dropping out of the' main direction switch and thew main brake and field switch to permit the immediate'change of connections for the field windings and thus slow down the elevator motor more rapidly., In this manner the tendency forthe car to overrun the floor is reduce i Should an overrun occur, however, the system is arranged so that the operation of the switches is modiiied, Assuming inthe above example that the car overruns the third fioor landing to the extent of causing the engagement of leveling switch down slow speed contacts 35, a circuit is completed for down leveling direction switch actuating coil LC228 and coil LH190. This circuit may be traced from't-he left-hand blade of switch 47, by way of line 55 through contacts A60, line 191, contacts 35, by way of' line 230 through coil LC228, by way'of line 192 through coil LH190, line 85, to the ri Aht-hand blade of switch 47 -as previously traced. Contacts LH205, LH206 and LH212 are {separa-ted and contacts LH207, LH208 and LH210 are engaged so that the circuit for resistance 33 across the brake release, coil is broken, the

generator main field winding is disconnected from the generator armature, the brake release coil is energized, resistance section 54 for the elevator motor field winding is shortcircuited andthe holding coils ofthe residual compensating switches are energized. Contacts LH212 insure the dropping out of the main direction switch. The switch LG operates to cause the separation of contacts LC133 and the engagement of contacts LC231, LC232 and LC233. The separation of contacts .LC133 is without particular effect at thisltime. The engagement of contacts LC231 and LC232 connects the auxiliary iield winding to the mains. Due to the reversal of the flow of current through the auxiliary iield winding from' that during the leveling operation with the car approaching the Hoor in the up direction, the car is caused to start in the down direction. Since relay LF is not operated, resistance 28 is included in the circuit for the auxiliary field winding, causing the motor to run at slow leveling speed. Since the generator E. M. F., during the return of the car to the landing, does not rise to theipredetermined value at which the down residual compensating switch is d'esigned to operate, resist-ance 39 remainsv short-circuited.

The engagement of contacts LC233 completed a circuit for the down series field relay actuating coil G234 and the down hard brake switch actuating coil P227. This circuit may be traced from the left-hand blade of switch 47, by way ot' line 55 through contacts A60,',by way ofline 235 through contacts LC233, coil G234, coil P237 and portion f 236 of reactance X203, line 204, lby way of line 58' through contacts A61, to the righthand blade of switch 47. Relay G and switch P do not operate'immediately upon the engagement .of contacts LC233. When approaching the floor in the up direction, the current flowing through reactance portion 202 caused a ilux to be built up in the reactance X203 in one direction.y Upon the separation of contacts LB197, the current in the reactance and kcoil P200 discharged into resistance 226 tending to maintain the flux built up and, as previously explained, switch 'P in operated condition. Upon the engagement of contacts LC233 on the overrun, the

l MQ; g l

current supplied to coils G2234 and P237 must reverse the flux in the reactance, thus taking a longer time to build up to a value sucient to cause the operation of relay G and switch P. Thus contacts F225, depending for their operation upon the operation of relay G, remains closed momentarily to insure that the current in the generator armature-motor armature circuit has fallen to a low value. Since the current in the series field winding may be flowing in a direction such as to cause the generation of scribed for approaching the floor in the up direction.

If the overrun is great enough to cause the engagement of the leveling switch down fast speed contacts 37 as well as the leveling switch down slow speed contacts 35, coil L`F193 is energized. As before, relay LF causes the engagement of contacts LF213- to short-circuit resistance 28, increasing the generator voltage and causing the elevator motor to run at its fast leveling speed.V Relay LF also causes the engagement of contacts LF214 to energize coil J 82 again in the event that it has become deenergized. Upon such an overrun, the automatic gate and door openingoperation does not occur until contacts LF214 separate, as previously described. Further than this, the operation 0n an overrun is as above described.

It is to be understood that the operator may control both the acceleration and retardation of the car by moving the car switch in steps. Should the operator sud denly move the car switch from one position into the other, for example from up'into d own position, injury tothe system is prevented by contacts B110 which remain separated until the up direction switch drops asl out. It is to be noted that, when the car is suddenly reversed or stopped between floors or stopped by opening the safety switch 50, the switch P is not operated. .Thus contacts P221 are in engagement and a soft application of the brakeis obtained.

During the leveling period, where the same values of current supplied to the generator field winding upon an underrun as during the return after an overrun, the E. M f F. generated might vary over awide range due to the varying'eifects of residual flux. As these current values would be relatively small, the residual flux present would forma large percentage of the total fiux and therefore might affect the operation of the systemf` very markedly. In order that the eiects of. the residual flux may be clearlyseen, reference may be lhad to the assumed khysteresis curvetshown in Figure 3.- vThis figure illustrates the conditions whe'nlja small current is supplled to the separately Aexcited field winding of a generator, as during the leveling operation. 'The magnetizing forces and that later, in attempting to make a landing, the self-leveling operation takes place with the car approaching the Hoor-f The E. M. F. of the generator during this period will be of a value V2. On the other hand, if t-he car. overruns the floor, the E. M. F. of the generator will be of a value V3, which value is much less than the value V2. Hence the speed of the elevator car is much less. rlhe values V2 vand V3 of the generator E. M. F. may vary during the operation of the system depending upon the previous magnetic state of the machine. Obviously, such large voltage variations would result in undesirable variations' in operation under leveling conditions. These variations cannot be satisfactorily corrected merely by adjusting the amount of resistance in series with the. field winding. F ory example, if the amount of resistance were decreased in order to raise the value of V3, the value of V2 also would be increased, resulting in an increasing tendency to run past tlie floor. Similarly, if the amount of resistance were increased in order to lower the value of V2, the value of V3 also would be lowered, which value might be too low to elfect the return of the car to the floor after an overrun,

In the present system, variations in operation of the car due to the effects of hysteresis are overcome by means of the residual compensating switches UR and DR and resistances 19 and 39. As has previously been set forth, switch UR operates only when the car is moving in the up direction and switch DR only when it is moving in the down direction. Also the actuating coils of the switches are set so that the switches do not operate. unless the generator E. M.-F. rises to a certain value. This value isgreater than that of .the generator E. M. F. during the'leveling perioda Thus the switch UR operates to remove the short circuit for resistance 19 when the car is moving upwardly during car switch operation but does not operate to do so during the leveling period when the car is moving upwardly to return to the. Hooi1 after an overrun in the down direction. Similarly, the switch DR operates towremove the short circuit for resistance 89 when the car is moving downwardly during car switch operation but does not operate to do so during the leveling period when the car is moving downwardly to return to the floor after anoverrun in the up direction. chosen so that it is effective to weaken the generatorield during leveling to the extent that V2 is substantially equal to Va under average conditions of the previous magnetic state of themachine, assuming`that V2 is the value of generator E. M. F. for movement of the car in up direction and V3 the value for returning the car to the floor after an overrun in the up direction. 1f thecar The value of resistance 19 is' therefore, the value of resistance 39 is chosen so that the value of V 4 is substantially equal to V5. The net result of this arrangement is to energize the field winding of the generator to a less extent when leveling in the same ldirection as the last car switch run than when leveling in the opposite direction, ths compensating for the eifectlof the residual magnetism of the generator. With the effects of residual flux eliminated, the system may be easily adjusted so as to give uniforml operation under leveling conditions.

Obviously operating conditions may arise, such as during leveling after .slow speed car switch operation, where the residual magnetism of the generator would not cause undesirable variations in the operation ofthe car. By adjustment of the residual compensating switch* actuating coils UR118 and Dlt121 to cause the operation of the switches only after the vgenerator E. M. F. has risen to a predetermined value, the system may be arranged so that compensation is had only when the residual magnetism would have an effect such as would prevent eflicient operation ofthe car under leveling conditions. It is to be noted that once either ofthe residual compensating switches is operated it is maintained operated so long as the car is running or leveling due to contacts LH210 ley-passing vcontacts H120. Should conditions arise to cause the separation of contacts H120 before the engagement of lcontacts LH210, suoli as might be caused by t00 early centering of car switch as previously indicated, the residual compensating switch is 'held in operated condition until contacts LH210 engage,due to the effect of reactance X220 and discharge resistance 128. In this manner the compensating resistance remains in circuit so long as the leveling continues .so as to weaken the generator field whenever the car moves in the same direction as its last high speedrun. It is to be noted, however, that the maintaining of contacts UR210 separatedA during the return of the car to the landing after an overrun in the up direction and contacts DR241 separated during the return after an overrun in the down direction has no effect as the circuits inl which these contacts are arranged are broken by the leveling direction switch' contacts. Although the compensating resistances are illustrated as arranged for inclusion inthe auxiliary field winding circuit, it is to be understood that they maybe arranged for flux and load.- Only such portion of the control system as relates to the residual and load compensating arrangement is illustrated in this ligure, it being understood thatv the remainder of the system may be arranged as illustrated in Figure 1. In this.`

figure, the actuating coils for the compensating switches may be arranged as current coils 1n the generator' armature-motor armature circuit and are designated UR25O and DR251. The polarities are arranged so that up motor current causes the operation of the down compensating switch DR and down motor current causes the operation of the'up 'compensating' switch .UR In the explanation which follows, up'current and down current will be used to designate currents producing up and down torques respectively in the elevator motor armature regardless of whether they are regenerative or motor currents. Each actuating coil is adjusted so as to cause the operation of the switch upon the current" to which it responds reaching a certain value.

Thus, assuming an overcounterweighted system, with balanced loa-d in the car running'up, switch DR operates when the car starts. During slow down however, the down or regenerative current. causes switch DR to drop out, coil DR251 oppos# ing holding coil DR218, and the operation ot switch UR to remove the short circuit for up compensating resistance 19. Similar opera-tion is had in the event of balanced load in a down moving car, the short circuit for down compensating `resistance '39 being removed during the slow down period. Thus compensation is ,had for the effect of residual flux the sameI as when the volta-ge coils URllS and DR121 were used. If, however, the car is running up with full load,`then the down current on stopping is not large enough to cause either the drop ping out of switch DR or the operation of switch UR. Thus, under such condition, the generator field for leveling, due to the separately excited winding. is strong for up movement of the car and weak for down movement, switch DR being held in by' the effect of reactance X220 andv discharge resistance 128 upon the overrun, aiding in bringing the car tol a. levelwith the landing. Similarly the switches operate to cause a strong vgenerator field :tor down movement of the car and a weak field tor up movement during leveling when the car has been running down with light load in the car. 1n running' empty car up and full load down,

the operation is substantially the same as described for balanced load in the car.

It is to be understood that other arrangements may be employed to obtain compensation for both residual iux and load, one of such arrangements being illustrated in Figure 5. As in thecase of the arrangement shown in Figure 4, only such portion 'of the control. system'as relates to the compensa-ting arrangement is illustrated in Figure 5, it being understood that the remainder of the system may be-arranged as illustrated in Figure 1. Three additional electromagnetic switches are illustrated in this system, these switches being designated as follows:

Q-load switch, QR-load relay, HR- hold-overrelay.

The load switch Q is provided with a current coil Q26() arranged in the generator armature-motor armature circuit and a voltage coil Q261 connected to the generator ar. mature. These coils act cumulatively when the elevator motor is lifting a' load and are set to cause the operation of the lload switch upon certain load conditions being obtained, these conditions varying with the diiferent installations. The actuating coil HR262 of the hold-over relay is arranged in series relation with the brake release coil 30. The

actuating Ycoils of the compensating switches UR and DR are arranged to be connected across lines -58 and are controlled by additional contacts provided on the main ,direction switches. The compensating switches are not provided with holding coils as in the systems previously described but are maintained in operated condition by the holdover relay andgby resistances 263 and 264 arranged to byy-pass the additional contacts B270 and C275 of the main direction switches. The load relay QR, controlled by the contacts Q269 of the load switch Q, is similarly maintained in operated condition by the hold-over relay and by resistance 265 arranged to by-pass the load switch contacts. x

During the operation of starting the car in the up direction, the operatio-n of the main brake and field switch H to cause the engagement of its contacts H124 completes the circuit for the hold-over relay actuating coil HR262 as well as the brake release coil. The hold-over relay operates to cause the engagement of its contacts HR266 in a circuit common to the actuating coils UR267 and DR268 of the compensating switches. At the same time the operation of the up main direction switch causes the engagement of aforementioned additional contacts B27() so that the circuit tor the up compensating switch actuating coil TTR-267 is completed. This circuit may be traced from line 55, by line 271. by way of line V272 through coil UR267 and contacts B270, by way of line 1,eeo,771

273 through contacts HR266, to line 58. The up compensating switch UR, upon operation, causes the engagement of contacts UR274. The purpose of these contacts will be explained during the description of a stopping operation.

During the operation of starting the car in the down direction, the circuit for 'the down compensating'switch actuating coil DR268 is completed by the engagement of hold-over relay contacts HR266 and down main direction switch additional contacts C275. This circuit may be traced from line 55, by line 271, by way of line 276 through coil 13R-268 and contacts C27 5, line 277 ,v by vcay yof linev 278 through contacts HR266, to line 58. The down compensating switch i DR, upon operation, causes the engagement of contacts DR278. The purpose of these contacts also will be explained during the description of a stopping operation.

It is to be understood that the ohmic values of resistances 263, 264 and 265 are such as to permit the passage of sutiicient current through their respective coils to cause the compensating switches and load relay to be maintained operated but not enough to cause their operation. Thus, with hold-over relay contacts HR266 in engagement., the down compensating switch does not operated-tiring the starting of the car in the up direction and the up compen-4 sating switch does not operate during the starting of the car in the down direction. Also the load relay QR does not operate unless the load switch Q, operates vto cause the engagement of contacts @269.

Thus, assuming an overcounterweighted system, under conditions of empty car running u wardly, the up compensating switch UR is operated, causing contacts UR274 to be in engagement, but the load switch Q is not operated and, therefore, the load relay QR is not. operated. Thus the load relay contacts @R280 and @R281 remain separated and contacts QR282 and @R283 rc'- main in engagement. During stopping, upon the dropping out .of the up main direction switch; B to separate contacts B270, the up compensating switch UR is maintained operated by current passing through its actuatinv coil .and resistance 268. Assuming that the car'underruns the floor, the leveling arrangement acts as previously described to cause the completion ot the circuit for the auxiliary `iield .winding 18. Although up compensating switch contacts UR274 are maintained in engagement, load relay contacts QR280 are separated so that the circuit for the auxiliary held winding includes up compensating resistance 19. This circuit may be traced from line 55, by way oi line 215 through contacts H122, contacts LF218 (assuming tast speed level- -iug operation), contacts LB195 and resistance 19, field winding 18, by way of line 284 through contacts LB196, to line 58.

Should an overrun occur, the up compensating switch i's maintained operated` b the hold-over relay co'ntacts HR266 remalning in4 engagement. The hold-over relay is maintained in operated condition, should there be an interval that 'the vbrake release coil 30 and coil HR262 are disconnected from the mains, by the brake release coil discharge current. It is to be noted that, with up compensating switch contacts UR274 and loadvrelay contacts QR288 in engagement, down compensating resistance 39 is short-circuited. Thus, upon the operation ,of the down leveling direction switch/LC to effect the return ot' the car to the landing", the circuit completed for the auxiliary field winding 18 does not include a compensating resistance and may be traced by way of line 284 through contacts LC231, lield winding 18, line 215 (to the left), by way of line 285 through contacts TIR-274, by way of line 286 through contacts QR283, line 287, back to line 215 and by way thereof through contacts LC232.

Similar operation is had whenthe car is moving downwardly with heavy load. in this case the down compensating switch is operated, causing contacts DR278 -to be in engagement, but the load switch (Q, is not operated and, therefore, the load relay QR is not operated. Thus, as above, the load relay contacts QR280 and @R281 remain separated and contacts @R282 and @R283 remain in engagement During stopping, upon the dropping out ot the down main direction switch C to separate contacts C275, the down compensating switch is maintained operated by the current passing through its actuating coil and resistance 264. Assuming that the car underruns the floor, the leveling arrangement acts to cause the completion of the circuit for the auxiliary field winding 18, the circuit including down compensating resistance 39 because the circuit prepared by contacts DR278 to short-circuit this resistance is open at contacts @l-281.

'The circuit for the auxiliary held winding under these conditions may be traced from line 55, by way of line215 through contacts H122 andcontacts Ll`213 (assuming :tastl speed leveling operation), by way of line 284 through contacts LC281, field winding 18, back lto line 215 and by way thereof through resistance 89 and contacts LC232, to line 58.

Should an overrun occur, the down compensating switch is maintained operated by the hold-over relay as described in connection with' an overrun in the up direction. As up compensating resistance 19 is shortcircuitcd by load relay contacts @R282 and down compensating switch contacts DR278, the circuit for the auxiliary iield winding 18, completed by the operation of the up levelin direction switch LB to effect the return o the car to the landing, does not include a compensating resistance and may be traced by Way of line 215 through contacts LB195, by way of line 287 through contacts QR282, by Way of line 288 through contacts DR278, field' Winding 18, by Way of line 284 through contacts LB196.

Thus, under the above describedv conditions, compensation is had for the effects of residual flux the same as When the voltage coils Uli-118 and DR121 of Figure 1 were used.

In the event of the load on the elevator motor being such as to cause the operation of the load switch Q, as Where an 'up moving car is fully loaded or when a down moving car is empty, load switch contacts Q269 engage, completing a circuit for the load relay actuating coil Q,R290. This circuit may be traced from line 55, by-Way of line 277 through coil QR290 and contacts Q269, by Way of line 27 3 through contacts HR226, to line 58.` With the `load relay operated, contacts (QB-280 and QR281 are in engagement and contacts QR282 and QR283 are separated.'

Thus, if the car is running up with full load, contacts UR274 and @R280 being in engagement and contacts QR283 being separated, resistance 19 is short-circuited While the short-circuit previously described for resistance 39 is broken so that, upon an underrun, up compensating resistance 19 is not included in the circuit completed for the' auxiliary field winding 18 to effect the bringing ofthe car to the floor While, upon an overrun, down compensating resistance 39.

is included in the circuit completed for the auxiliary field Winding 18 to effect the return of the car to the floor. Thus, as in the case of the systemillustrated in Figure Ll, when the car has been running up with heavy load, the generator. field for leveling, created by the separately. excited Winding, is strong for up movement of the car and Weak forv down movement. In a similar manner,

. a strong generator field for down movement of the car and a Weak field for up movement is obtained for leveling When the car has been running down with light load. Under these conditions resistance 39 lis short-circuited by contacts DR278 and Q,R281 and the prevlously described short-circuit for resistance 19 1s broken by contacts @R282 being separated.

As many changes could be made in ,the above arrangements and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that lall matter contained in the above description or shown 'in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In combination; an elevator car; a hoisting motor therefor; a -generatoryfor supplying current to said motor, said generator having a field Winding; `means for causing said motor to level the car with a desired landing in stopping, regardless of Whether it underruns or overruns the landing; and means for causing the application of less voltage to said field-Winding upon the operation of the first named means to cause the motor to bring thecar to the landing upon an underrun than upon the operation of the first named means to cause the motor to return the car to the landing after an overrun.-

` 2. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current to the motor, said generator having a field Winding; a source of curvrent for said field Winding; and means for `Whether it underruns or overruns the landing, said last included means comprising means ,for causing less current to fioW through said field winding when itis connected for effecting the bringing'of the car to the landing upon an underrun than when it is connected for effecting the return of the car to the landing after an overrun.

3. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current to said motor, said generator having a field Winding; a source of current; a resistance; and means for causing said motor to level the car with a desired landing in stopping, regardless of Whether it underruns or overruns the landing, .said means comprising means for connecting said field winding to said source in circuitvvith said resistance When the car is.

to be brought to the landing upon an underrun and means for lconnecting said field vvindingto said source Without said resistance in circuit when the car is to be returned to the landing after anoverrun.

4c. In combination; an elevator car; a hoisting `motor therefor; a generator for supplying current to the motor, said generator having a field vvinding; a source of current; a resistance; means for causing the motor to level the car With a desired landing in stopping, regardless of Whether it underruns or overruns the landing, said means comprising 'means for. connecting said field winding to said source; and means for compensating for the effects of the residual magnetism of the generator, said lastl named means comprising means for inserting said resistance in circuit with said field Winding for the operation of the first named means to cause movement of the car in the direction that it was moving before the operation of the first named means.

I means,`said last named means comprising means for inserting oneof Said resistances `in circuit with said field Winding for the operation-ofthe first named means to effect v the bringing of the car to the landing in one direction upon anunderrun vand for inserting the other resistance in circuit with said field Winding for the operation of the first named ymeans to effect thefbringing of the car to the landing in the other direction upon anunderrun. f

6. I11 combination; an elevator car; a

hoisting motor therefor; a generator for supplying current to said motor, said generator having a main field Winding and an auxiliary field Winding; asource of current; means forconnecting said main field winding to said source for ful-l speed operation; means for causing the motor to level the car with a desired landing in stopping, regardless of whetherfit underruns or overruns the landing, said second named means comprising means ffnconnecting said auxiliary field winding to said source; and kmeans for causfing less current to be supplied from said' source to said auxiliary field winding during the operation ofthe second named means to cause the motor to bring the car to the landing upon an underrun than is supplied from said source to the said auxiliary field Winding during the operation of the second named means to fcause the motor to return the car to the landing after an overrun.

7. In combination, an elevator car; a hoisting motor therefor; a generator for supplying current to said motor, said generator havinga main field winding and an auxiliary field winding; a source of current;

Y f means for starting said motor, said means y comprising means for connecting said main field Winding to said source at a reduced voltage and thereafter increasing the voltage so as to bring the motor up to full speed;

" means for causing said motor to level the car with a desired landing in stopping, re-v` gardless of Whether it underruns or overruns the landing, said second named means comprising means for disconnecting said main field Winding from saidsource and for o connecting the auxiliary field Winding thereto to cause the motor to run at a-fast leveling speed, a resistance, and means for inserting said resistance in circuit with said auxiliaryjlicld winding as the car nears the landing to cause the motor to run at a slowr leveling speed; a pair of additional resistances; and means for inserting one of said additional resistances in circuit with said auxiliary field winding for the operation of the second named means to effect the bringing of the cai to the landing in one direction upon an underriui and for inserting the otl1er`additional resistance' in circuit With said auxiliary field Winding for the operation of the second named means to effect the bringing of tbe car to the landing in the other direction upon an underrun.y

8. In combination; an elevator car; a hoisting motor therefor; a generator for supplying ycurrent to said motor, said generator having a field Winding;x means for causing'the motor to level the car with a desired landing in stopping, regardless. of Whether it underruns or overruns the landing; and means for'causing, under-certain load conditions, the application of less voltage to said'field Winding upon the operation of the first named means to' cause the motor to bring the car to the landing upon an underrun than upon the operation` ofthe first nainedfmeans Vto `cause the motor 'to return the car to the landing after an overrun and for causing, under other loadconditions,

'the application lof less voltageto said field Winding upon the operation bof the Vfirst named means to cause the motor to return the car to the landing after an overrun than upon the operation of the first named means to cause the motor to bring the car to the landing upon an underrun.

9. ln combination; an elevator car; a hoisting motor therefor; a generator for supplying current to said motor,-said generator having a field Winding; means for causing the motor to level the car with a desired landing in stopping,v regardless of Whether it underruns or overruns the landing; means for causing the application of less voltage to` said field Windingupon the operation of the `first named means ,to cause the motor to bring the car to the landing upon an underrun than upon the operation of the first 'named means to cause the motor to return the car to the landing after an overrun; and means responsive to the load on said motor for causing the application of less voltage to said field Winding upon the operation of the first named means to cause the motor to returnv the car to the landing after an` overrun than upon the operation of the first named means to cause the motor to bring the car to the landing upon an underrun. l

l0. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current to said motor, Said generator having a field winding; means for causing the motorto level the car with a desired landing in stopping, regardless of Whether it underrunsr or overruns the landing; means for causing the application of less voltage to said field Winding upon the operation of the first named means to cause the motor to bring the carto the landing upon an underrun than upon the operation of' the first named means to cause themotor,

supplying current to said motor, said generator having? afield Winding; means for causing the motor to level the ca'r with a desired landing in stopping, regardless of Whether it underruns or overruns the landing; means for causing` the application of less voltage to said field Winding upon the operation of' the first namedmeans to cause the` motorto 'bring the car to the landing upon an underrun than upon the operation of the first named means. to cause-the motor 'to return the car to the landing after anoverrun; and load responsive means for causing decreased voltage to be applied to said field Winding upon the operation of' `the first named means tocause the motor to return the vcar to the landing after an overrun.

12. In combination; an elevator car; a hoisting motor therefor; a generator for supplymg current to said motor, said generator having a. field winding; means for causing the motorA to level the car with a desired landing in stopping, regardless of v whethery it underruns or overruns the landing; means for causing the application of less voltage to said fieldfwinding upon the l Y Y operation of the rst named means to cause the motor to bring the car to the landingr upon an underrun than upon the operation of thefirst named means to cause the motor to return the car to the landing after an overrun; and means responsive to. the load on said motor for causing increased voltage to be applied to said field Winding upon the operation of the first named means to cause the motor to bring the car to the landing upon'an underrun and decreased voltage to be applied to said. field winding upon the operation of the first named means to cause the motorv to return the car to the landing -after an overrun.

13. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current'to said motor, said generator having a field Winding; a source of current for said winding; means for causing the motor to level the car with a desired landlngin stopping, regardless of whether it underruns or overruns the landing; means for causing less current to be supplied from said source to-said field Winding during the operation of the first named means to cause theA motor to bring the car to the landing upon an underrun than is supplied from said source to said field Winding during the operation of thefirst named means' to cause the motor to return the car tothe landing after an overrun; and load responsive means for causing more current to be supplied from said source to said field Winding during the operation of the first named means to cause the motor to bring the car to the landing upon an underrun than is' supplied from said source to said field Winding during the operation of the first named means to cause the motor to return the car to the landing after an overrun. p

14. In combination; an elevator car; a hoisting motor therefor; a generator for supplying current to said motor, said generator having a field Winding; a source of current for said Winding; means for causing the motor to level the car With a desired landing in stopping, regardless of Whether it underruns or overruns the landing; means for causing less current to be supplied from said source to said field Winding during the operation of the first named means to cause .the motor to Ibring the car to the landing upon an underrun than is supplied from ysaid source to said field Winding during the loperation of the first named means to cause the motor to return the car to the landing after an overrun; andmeans responsive to the loadpon the motor prior to the operation of' the first named means for causing more current to be supplied from' said source to said field Winding during the operation of the first named means to cause the motor to bring the carto the llanding upon an underrun than is supplied from said-source to said field winding during the operation of the first named means to cause the motor to return the car to the landing after an overrun. y

15. In combinationyan elevator car; a hoisting motor therefor; a generator Afor supplying current to said motor, said generator having a field Winding; a source of current; a resistance; .means for causing said motor to level-.the car with a desired landing in stopping, regardless of whether it underruns or overruns the landing, said means ycomprising means for connecting said field Winding to' said `source in circuit with said resistance. when "the car is to be brought to the landing upon an underrun;..and load responsive means for, preventing the inclusion of said resistance in said circuit.

- 16. In combination; an elevator car; a

hoisting motor therefor; va generator for.

supplying .current to said motor, said generator having a. field winding; a source' of current; a resistance; means for causing said Amotor to level the c ar with a desired landp field Winding to said source in circuit With said resistance when the car is lto be brought.

to the landing in one direction upon an underrun and means for connecting said field Winding to said source without said resistance in circuit when the `car is to be returned to the landing in said one direction after-an overrun; and means responsive to the load .on the motor lprior to the operation of the first named means for preventing the inclusion of said resistance in circuit with said field winding when connectedv for bringing the car to the landing 'in said one direction u on an underrun and for causing the inc usion' of said resistance in circuit with said field Winding `when connected 'for returning the car to the-landing in said one direction after an overrun. y

17. In combination; an elevator car; a hoistin motor therefor;` a lgenerator' for supplying current to said motor, said generator'having ay iield winding; means for causing the motor to level the car VWith a desired landing in stopping7 regardless of Whether it underruns or overruns the landing; a pair of resistanes; means ior causin g the inclusion of one of said resistances in circuit with said iield Winding for the operation yof the first named means to effect the bringing in one 1011 uponl an underrun and for causing the inclusion of theother resistance in circuit with said field winding for the operation ofthe rst'named means to effect the bringing of the car to the landing in the other' direction upon an underrun; and means yresponsive to the load on the motor for preventing the inclusion of said one resistance in circuit with said field winding for the o eration of the first named means to effeet t e bringing of the car to the landing in one direction upon` an underrun and of said Yother resistance in circuit with said field fwinding for the operation of the first named means to effect the bringing of the car to the landing in the other direction upon an underhoisting In combination; an elevator car; a motor therefor' a generator for supplying current to said motor, said gena erator having a eld winding; means for causing the motor to level the car with a` desired landing in stopping, regardless of whether it underruns or overruns the landing; a air of resistances; means for causing the inc usion of one of said resistances in circuit with said field winding for the operation of the first named means to effect the bringing of the car to the landing in one direction upon an vunderrun and for causing of the car to the landingthe inclusion of the other resistance in circuit with said field Winding for the operation of the first named means to effect the bringing of the car to the landing in the other direction upon an underrun; and means responsive to the load on the motor for preventing the inclusion of said one resistance in circuit with said field Winding for the operation oi the first named means to eect Ythe bringing of 'the car to the landing in one direction uponI an underrun and of said other resistance -in circuit With said field winding for the 'operation of the first named means to effect the bringing of the car to the landing in the other direction upon an underrun and for causing the inclusion of said one re- -sistance in circuit with said iield Winding for the operationof the first named means to effect the returning of thecar in said one direction to the landing' after an overrun land the inclusion of said other resistance in circuit with said field winding for the operation of the first named means to eiect the returning of the car in saidk other direcv tion to said landing after an overrun.

19. In combination; an elevator car; a hoisting motor therefor; a generator for supplyi'ng current to said motor, said generator having a main field Winding and an auxiliary `:tield Winding; a source of current; means for starting said motor, said means compris- Whether it underrun-sl or overruns said landing, said second named means comprising means for disconnecting said, main field Winding from said source and'for connecting the auxiliary field Winding thereto; means for causing less current to be supplied from said source to said auxiliary field Winding during 'the operation ofthe second named means to cause themotor tobring the car to the landing upon an underrun than is supplied from said sou'rce `to` said auxiliary field windin during the operation of the second namedg means to cause the motor to return the car to the landing after an overrun; and load responsive means for causing more current to be supplied from said source to said auxiliary iield winding during theoperation of the second named means to cause the motor-to bring the car to the landing upon an underrun than is supplied froml said source'to said auxiliary field winding during the operation of the second named means to cause the motor to return the car to the landing after an overrun.

20. In combination; anA elevator car; a hoisting motor therefor; a generator for supplying current to said motor', said generator having a main field winding and an 

